1. Field of the Invention
This invention relates to bowl shaped products, and processes, equipment and materials for manufacturing bowl shaped products comprising plastics, preferably mainly acrylic plastics and including alumina trihydrate therein as a filler.
2. Description of the Related Prior Art
Kitchen, bathroom and office countertops fabricated from flat sheet stock of solid surfacing material comprising acrylics filled with alumina trihydrate such as that sold under the trademark of "Corian", manufactured by E.I. duPont de Nemours & Co., Inc. of Wilmington, Del. 19898 U.S.A., have been in use now for many years. "Corian" is a trademark of E.I. duPont de Nemours & Co., Inc. which refers to their solid surfacing material comprising acrylics filled with alumina trihydrate, alternatively referred to as aluminum trihydrate, the alumina trihydrate comprising 20 to 85 percent by weight of the solid surface material or article. Other companies are now also manufacturing and selling rigid sheet stock solid surfacing material comprising acrylics filled with alumina trihydrate for use as building materials. Solid surfacing material comprising acrylic filled with alumina trihydrate is believed to be manufactured generally in accordance with the processes and mix formulas disclosed in U.S. Pat. No. 3,847,865 issued Nov. 12, 1974 to inventor Ray Duggins and assigned to E.I. duPont de Nemours & Co., Inc. Formulas (mixes), processes and principles thereof provided in U.S. Pat. No. 3,847,865 describe that acrylic resins (polymers) filled with 20 to 85% by weight alumina trihydrate, preferably 55 to 85 percent by weight alumina trihydrate, can be the basis for producing a quality building material having many desirable attributes, and desirable attributes beyond those provided by other similar mixes of substantially other plastics families and fillers other than alumina trihydrate, as described in U.S. Pat. No. 3,847,865. Duggins states that below an approximate 20 percent fill of alumina trihydrate in the plastics provides little benefit from the filler, and above an approximate 85 percent fill of alumina trihydrate and the mix generally cannot be formed into a hardened useful material. Duggins details in the U.S. Pat. No. 3,847,865 patent that the acrylic plastics are the primary binder and include desirable attributes including translucent qualities, and the alumina trihydrate is preferably applied in the range of 55 to 85% by weight of the article as a important filler for achieving certain qualities, and colorants such as pigments, pigmented particles and the like can be added to the mix to achieve various visual appearances including those simulating stone such as marble or those having a variegated pattern. It is also stated in the Duggins patent that various small quantities from other numerous plastics families can also be added to the acrylic and alumina trihydrate mix and for numerous reasons. Duggins also details how to form such a mix of acrylic binder with alumina trihydrate filler and colorants into material shapes by casting or extrusion to define building material shapes such as flat rigid sheet stock or to cast the fluid mixture into non-flat structures prior to solidification. The solid surfacing material today sold under the name of "Corian" is acrylic binder heavily filled with alumina trihydrate, possibly containing some small quantities other plastics, and in most varieties of the mix including various colorants as described in the Duggins patent. It is believed that "Corian" solid surfacing material in rigid sheet form sold today for countertop material is manufactured with an approximate 70% by weight fill of alumina trihydrate in a binder of primarily acrylic plastics and including pigments, organic and/or inorganic, (and possibly dyes in some cases for some colors) dependant upon desired visual affect. Concentrations of the alumina trihydrate between 55 and 85 percent in the plastics provides greater hardness and resistance to flame, as opposed to lower concentrations. Variations of the formula, mainly in the colorants used, provide such solid surfacing material in a wide variety of different appearances in flat sheet stock for use as building materials. Solid surfacing materials of acrylic filled with alumina trihydrate are most often manufactured and sold in flat rigid sheet form, typically in 30 inch wide .times.12 foot lengths in thicknesses between 1/4 through 3/4 inches and also in metric sizes, and in many different solid colors, color design patterns, i.e., having veining of different colors or shades of colors therein, and matrix colors or appearances, i.e., clearly distinguishable granular or particle-like color variations, and in some cases appearing as various types of natural stone. Flat sheet stock of such acrylic filled with alumina trihydrate and colorants is believed to be initially cast as a thick fluid or mix, then solidified, and then for most color mixes, sanded and polished (faced) on at least the side of the sheet intended to be exposed in use, although the Duggins U.S. Pat. No. 3,847,865 also describes the material mix as extrudable as a mix prior to solidification. The facing, i.e., sanding or any like process of the cast solidified flat sheet is to mechanically remove a thin outermost surface layer or skin-layer which, generally due to settling of colorants and some upward migration of translucent materials of the mix, does not appear the same as the balance of the sheet acrylic filled with alumina trihydrate and colorants, which as will be discussed, is a problem in economically casting such material in certain colors in three-dimensional or bowl shapes since it is clearly much easier to sand a rigid flat surface compared to the rigid multiple curved surfaces of three-dimensional products. It is believed that certain colors of the acrylic filled with alumina trihydrate material, particularly the solid colors defined with very small and evenly distributed particles and colorants can be cast or extruded without the requirement of any or any significant amount of later sanding to achieve a basically finished surface and appearance, while other color mixes of the material require substantial amounts of sanding after solidification to eliminate the skin surface layer not appearing like the balance of the material. As previously stated, in the prior art, acrylic filled with alumina trihydrate has been cast, initially as a thick fluid into bowl forms for use as sinks and lavatories, some bowls cast with integrally cast countertops to define one-piece sinks/countertop units. However, three-dimensional cast bowls such as lavatories comprising acrylic filled with alumina trihydrate for mounting within a countertop are not economically obtainable in as a wide of a variety of colors and color design patterns and matrix colors as the same material in sheet form. This is believed to be due to increased difficulties in 3-D casting and finishing (sanding and polishing) compared to flat sheet formation, particularly with controlling colorant, pigment and color particle dispersement and final position thereof within the mix when the mix is fluid and pushed into and then held in a three-dimensional shaped casting mold prior to the mix solidifying, such as by catalytic action. There has been limited success, generally restricted to only certain colors, using matched mold casting of acrylic binding a filler of alumina trihydrate by forcing the mix into a bowl shaped casting cavity, then allowing or causing the material to solidify (polymerize or thermoset, such as with injection of a catalyst) prior to removing the bowl from the casting tool. It is believed significant amounts of sanding and polishing are required for most colors after the cast bowl is removed from the cast mold, and machining of at least a bottom drain hole and optionally an overflow opening is required if the bowl is to be used as a water basin. The casting process of the prior art has, however, due to colorant settling (migration) and sanding and polishing requirements, not been a completely satisfactory and economical process for producing bowls comprising acrylic plastics binding large amounts of alumina trihydrate in as wide of a variety of colors, color design patterns with color swirls and veining (venaro), and matrix colors including speckles or flakes as are available in flat sheet stock of the same material used for defining countertops.
Reasons for the growing popularity of solid surface material of acrylic filled with alumina trihydrate include the fact the material can be manufactured in flat sheet form to visually simulate certain types of stone, such as granite, jade, marble, or it can simply be manufactured in a variety of colors not intended to or said to simulate rock or stone. The color or color design patterns or color matrix of the sheet material is also deep or full thickness in the dense material, which allows various types of router or milling work (machining) thereto for initial installation such as when installing a countertop and making a sink cut-out in the countertop. It also allows removal of imperfections such as burn marks, scratches and the like by abrasives. The material is dense, solid, non-foamed and non-laminated, and so it can be readily machined, sanded and polished. Other reasons for the popularity of solid surface material comprising acrylic binding alumina trihydrate filler in flat sheet is that the material is hard and provides high durability, flame resistance, ease of damage repair, ease of cleaning and sterilization, beauty, color stability, resistance to deterioration from common household chemicals and cleaning agents, and resistance to cracking, all attributes which are clearly also desirable in bowls, e.g., lavatories, bar sinks, shower pans and the like water basins. Additionally, solid surface countertops of acrylic filled with alumina trihydrate may be fabricated of several adhesively bonded seamed sections and yet appear as a single and continuous countertop due to the seams being visually imperceptible when properly applied.
In the past, the public was somewhat restricted in color choice in bowls (water basins) made of acrylic plastics filled with alumina trihydrate, and somewhat restricted in color choice for their matching countertop and water basin when both were made of acrylic plastics filled with alumina trihydrate. Thus, prior to the present invention, the public has not been provided the ability to make a matching countertop and water basin without being somewhat restricted in color choice, because bowls of acrylic filled with alumina trihydrate were not available in as wide of a variety of colors, color patterns and matrix colors as is available in flat sheet form.
Clearly from the above, it can be appreciated that bowls, i.e., lavatories, bar sinks, shower pans and the like water basins, made of acrylic filled with alumina trihydrate would or could be high quality bowls having many highly desirable attributes. It can also be appreciated that it is desireable to have a wide choice of colors and color matrix or color design patterns in solid surface material bowls of acrylic filled with alumina trihydrate, and this even if one was not trying to visually match a countertop to the sink. Furthermore, it can be appreciated that it is desirable to have or be able to economically produce bowls comprising acrylic filled with alumina trihydrate of virtually any color or color pattern or matrix for visually matching flat sheet stock comprising acrylic filled with alumina trihydrate which could be used to define a countertop, thereby allowing the matching of the countertop and bowl in material, durability and appearance. It can also be appreciated that economical considerations such as the cost of producing a bowl of acrylic filled with alumina trihydrate are always a concern.
The prior art, prior to the present invention has widely used machining such as saws, sanders, routers and the like to cut, trim and shape flat rigid sheet stock of acrylic filled with alumina trihydrate and containing colorants. It is believed high pressure water jets and lasers have or can be used to cut or trim such material, although lasers will discolor the surface. The prior art, prior to the present invention has also seamed pieces of acrylic filled with alumina trihydrate using adhesives with the result being that the seams are imperceptible or virtually imperceptible. In the prior art, prior to the present invention, flat rigid sheet strips of acrylic filled with alumina trihydrate and including colorants have been heated to softening and bent along a single axis in the heated area to form long radius 90 degree (two-dimensional only) corner bends in otherwise flat sheets of the material, such bent corners being used lengthwise vertically installed in shower stalls as corners between flat sheet walling.
Possibly applicable prior art known to us, in addition to that above described, which might be considered relevant to the present invention generally falls into several categories, with a first being prior art describing machining, i.e., mechanical material removal including cutting, sawing, sanding, drilling with drill bits and hole saws, milling and mechanical shaping such as with routers, molders, end mills and the like, particularly of solid surface material comprising acrylic filled with alumina trihydrate. Some prior art in the first category, i.e., machining, which is considered cumulative to the above described prior art is located in the following U.S. Pat. Nos.: 4,958,888; 5,253,932; 5,359,817; 5,330,262; and 5,354,592, with each of these patents listing other prior art references which may be relevant to the present invention.
A second category pertaining to potentially applicable prior art relates to themoforming or heating of rigid plastics to first soften them and then applying force for re-shaping the heated plastics. Prior art in the second category, i.e., thermoforming, which is considered somewhat cumulative to the above admitted to prior art is located in the following U.S. Pat. Nos.: 3,172,928; 5,635,271; 5,340,526; 3,340,714; 4,239,727; 2,444,420; 3,464,418; 5,139,407; 2,590,221 and 4,136,226, with each of these patents listing other prior art references which may be relevant to the present invention. Admittedly the prior art in thermoforming details three-dimensional forming of heated sheets of various plastics families and including acrylics, however, it should be noted such prior art is not known to have suggested or anticipated the thermoforming of flat sheet stock comprising acrylic filled 20 to 85 percent or 55 to 85 percent by weight (preferred for building materials) with alumina trihydrate into three-dimensional bowl shaped products. Additionally, it should be noted the vast majority of prior art of thermoforming processes restrain or otherwise clamp the peripheral edges of the heated sheet during forming, with this placing the material under high tension and shear loads. Furthermore, many of the prior art thermoforming processes of the above listed patents assume a high degree of elasticity in the heated plastics and thus advocate edge clamping and forming the plastics with sharp angular changes such as curved sidewalls turning sharply outward and extending horizontally at the top of the form or bowl to define a flange, or short radius 90 degree corners such as where a curved vertical sidewall joins a flat bottom panel of the thermoformed article.
A third category of prior art is related to manufacturing or mixing acrylics filled with alumina trihydrate and including colorants such as the aforementioned Duggins U.S. Pat. No. 3,847,865. U.S. Pat. No. 4,473,673 is considered cumulative to the prior art information in the Duggins U.S. Pat. No. 3,847,865 pertaining to casting of fluid materials, but is specifically directed toward casting fluid mixtures substantially of a polyester resin base.
In our opinion, the prior art which might be considered relevant to the present invention does not describe or suggest the present invention and the many advantages provided by the invention.